Crystal structure and Hirshfeld surface analysis of 2,5-diimino-8a-methyl-4,9-bis(4-methylphenyl)-7-oxo-6-phenyl-decahydro-2H-3,8-methanopyrano[3,2-c]pyridine-3,4a-dicarbonitrile N,N-dimethylformamide monosolvate

Intermolecular C—H⋯O and C—H⋯N hydrogen bonds connect individual molecules into layers extending parallel to (100). These layers are connected by C—H⋯π interactions.


Chemical context
Different C-C, C-N, and C-O bond-formation methods play important roles in various organic synthesis directions (Aliyeva et al., 2011;Zubkov et al., 2018;Viswanathan et al., 2019;Mamedov et al., 2022). Heterocyclic systems, especially those comprising the pyrano[3,2-c]pyridine scaffold, are present in many natural or synthetic products with a wide spectrum of biological properties, such as antitumor, antitubercular, cholinesterase inhibitor and anti-diabetic activities (Mamedov et al., 2019;Kumari et al., 2018). One of the most effective synthetic approaches to these polyfunctional heterocyclic systems is a Michael addition of active methylene compounds at the ylidene malononitrile functionality (Girgis et al., 2015). In a recent study (Mamedov et al., 2019), we found that the reaction of two moles of arylidene malononitriles with acetoacetanilide in the presence of piperazine hydrate leads to the formation of novel tricyclic pyrano[3,2-c]pyridine derivatives at room temperature (Fig. 1).

Supramolecular features and Hirshfeld surface analysis
In the crystal, intermolecular C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds (Table 1) link individual molecules, forming layers parallel to (100) (Fig. 4). These layers are connected by C-HÁ Á Á interactions (Fig. 5). Interestingly, the imine C N-H groups are not involved in hydrogen-bonding interactions. The molecular entities of the title compound, showing the atom labelling and displacement ellipsoids drawn at the 30% probability level. C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds are indicated by dashed lines. Table 1 Hydrogen-bond geometry (Å , ).
A Hirshfeld surface analysis was performed to quantify the intermolecular interactions; the accompanying two-dimensional fingerprint plots were obtained using CrystalExplorer17 (Turner et al., 2017). The Hirshfeld surface mapped over d norm using a standard surface resolution with a fixed colour scale of À0.1713 (red) to 1.4361 (blue) a.u. is shown in Fig. 6. The shorter and longer contacts are indicated as red and blue spots, respectively, on the Hirshfeld surfaces, and contacts with distances approximately equal to the sum of the van der Waals radii are represented as white spots. The most important red spots on the d norm surface represent the aforementioned C-HÁ Á ÁO and C-HÁ Á ÁN interactions (Tables 1, 2).  A partial view of the crystal packing along the a axis of the title compound with C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds indicated (dashed lines). [Symmetry codes: (i) x, Ày + 1 2 , z À 3 2 ; (ii) x, Ày À 1 2 , z À 1 2 ].
Compounds (I) and (III) crystallize in monoclinic space groups (P2 1 /c, Z = 4, and P2 1 /n, Z = 4, respectively), whereas (II) is orthorhombic (Pbca, Z = 8). In each of the three structures, the bicyclic ring system adopts a chair/chair conformation and the phenyl rings are in equatorial orientations with respect to the piperidine ring. In (II), apart from van der Waals forces, only weak intermolecular C-HÁ Á ÁO-type interactions are involved in the packing.
In (V), which likewise is monoclinic (C2/c, Z = 8), the bicyclic ring system adopts a twin-chair conformation. The two methyl groups attached to the bicycle are in an equatorial orientation for both rings. In the crystal, very long N-HÁ Á ÁO hydrogen bonds connect the molecules into a chain perpendicular to [010].

Synthesis and crystallization
The title compound was synthesized using a previously reported procedure (Mamedov et al., 2019). Colourless crystals were obtained upon recrystallization from an ethanol/water (3:1 v/v) solution.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. All C-bound H atoms were placed at calculated positions and refined using a riding model, with C-H = 0.95-1.00 Å , and with U iso (H) = 1.2 or 1.5U eq (C). The N-bound H atoms were located from difference-Fourier maps and refined with free atomic coordinates and U iso = 1.2U eq (N).  Table 2 Summary of short interatomic contacts (Å ) in the title compound.